From USA Today: http://www.usatoday.com/story/opinion/2013/02/19/problems-falling-birth-rate/1931437/
Americans are realizing they are facing a demographic nightmare that has been looming in other Western nations for decades.
For the first time in history, fewer American babies are being born while the number of senior citizens is growing. Baby Boomers are reaching retirement age, increasing the ranks of the elderly. At the same time, women living without a spouse outnumber those who are married. The result is a birth rate in decline. If it were not for immigration, our nation would be in serious trouble.